Application of Maxima and Minima

Kindly help me with this problem.

Two post, one 8 ft high and the other 12 ft. high, stand 15 ft. apart. They are to be stayed by wires attached to a single stake at ground level, the wires running to the top of the posts. Where should the stake be placed to use the least amount of wire ?

Two post, one 8 ft high and the other 12 ft. high, stand 15 ft. apart.
They are to be stayed by wires attached to a single stake at ground level,
the wires running to the top of the posts.
Where should the stake be placed to use the least amount of wire ?